


A Nerd's 21st

by suckybuss



Category: Hesokuri Wars - Fandom, おそ松さん | Osomatsu-san (Anime)
Genre: Birthday, Birthday Sex, Dancing, Drunk Sex, F/M, Floor Sex, Gen, Gender Neutral, Lemon, M/M, Oral Sex, Self-Insert, musical AU, musical matsus
Language: English
Status: Completed
Published: 2019-08-06
Updated: 2019-08-06
Packaged: 2020-08-10 21:04:29
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,252
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20141974
Author URL: https://archiveofourown.org/users/suckybuss/pseuds/suckybuss
Summary: You and Karl Pinefield (aka Musical AU Karamatsu) go on a date for his 21st birthday, and his first sips of alcohol make him a bit frisky. You're barely in the door by the time you both get home before he can't restrain himself anymore. Gender neutral self insert w/fem parts.





	A Nerd's 21st

“HAPPY, HAPPY BIRTHDAY, IT’S (clap) YOUR VERY SPECIAL DAY!”

Karl’s face was scarlet red as a crown declaring him the “Birthday King” was placed onto his head; a formation of waitstaff surrounded your table, singing with all the fury of underpaid grad students, as you clutched onto his hand. 

You couldn’t take your eyes off him. Karl was surrounded on all sides by flustering situations; the embarrassing birthday dance, combined with being stared at by his adorable date… He couldn’t take it. He put one of his hands up to cover his face.

You giggle, looking away to give him a bit of reprieve, and squeeze his hand tightly. He lowers his hand and looks at you, his cheeks just getting hotter as he stares at you. 

The staff finish their song and dance and finally take your order; Karl, using a handkerchief to dab the sweat away from his forehead, allows you to place your order first as he fishes in his wallet for his brand-new driver’s license. 

“A-ahem… So, well, I happen to be turning twenty-one today,” he says, presenting the card to the waiter. “I’d like a double cheeseburger combo and, uh, uh, a Blue Bayou, please.”

“Sure thing,” says the waiter, scratching your orders down on their notepad. “Be right out with your drinks,” they say, turning to speed-walk to a bustling bar.

“Oh, I messed that up, didn’t I? I sounded dumb, right? Did I sound dumb?” Mumbles Karl, once again hiding his face in embarrassment; you squeeze onto the hand you’re holding with both of your hands, grinning gleefully.

“No, love! You were fine. No, better than that, you were wonderful.”

“Pssh, aww…” he says, his face just getting redder yet again. “You’re too nice to me.” He leans in to kiss you on the forehead.

Your dinner passes along wonderfully; there’s a reason you come to this place so often, the food is without comparison. Karl expresses his hesitation before taking a sip of the stunningly blue beverage in front of him; however, after the first sip, it doesn’t take much time for the glass to be emptied and for him to call over another one. You warn him to take it easy, it can sneak up on you the first time around; he gives you another playful kiss on the forehead and promises you that he’ll take it easy.

About an hour into your date, both you and him are feeling just a bit tipsy, and your fingers playfully intertwine and caress each other’s wrists. At this point, a few people have moved to the bar’s small dance floor, centered around a large colorful jukebox.

“So, my dear… Could I have the honor of a dance with you?” he says, stroking his fingertips gently down your arm. 

“Oh, but of course,” you playfully respond, sliding out of your chair and offering your elbow for him to hook his own onto. He stands, sliding his arm through your own, kissing you on the cheek in the process.

“I think I’ve got a couple quarters on me… You wanna choose the next song?” he offers.

“I’d love that,” you smile, accepting the quarter that he places gingerly in your palm. You walk over to the jukebox, slide in the quarter, and make your selection; something that you think ought to give him the right idea.

You bound back up to him, giddy in your slight intoxication, and meet him with an embrace. He holds you tight for a moment, savoring this one little taste of intimacy with you; and you pull away, swinging his arms along with the song that’s playing, and you both laugh as you try to match each other’s rhythm.

Not long after, your selection begins; “One on One” by Hall & Oates, a choice with unambiguous lyrics and a sensual rhythm. You wrap your arms around him to slow dance; he averts his gaze from you briefly, his face turning a little red again; but then he looks back at you, his expression easing into an adoring smile. He places his hands on your hips as you start to sway to the music.

“You’re… You’re just so incredibly beautiful, don’t you know that?” he says, leaning into your ear.

You giggle and respond “Thank you, handsome.” He brings his lips down onto your neck, giving you three gentle kisses that give your arms goosebumps.

“But… But you’re just… I’m just so… I’m so lucky to be with you. I’m so lucky to have you. You’re just so beautiful and cool and funny and-“ he’s interrupted by you coming in for a kiss, a warm, smiling kiss that makes him embrace you like his life depended on it; he grips onto your clothes in order to hold you extra tightly, and you spend a couple seconds like this, completely taken by each other.

You push back slightly, giggling and blushing, and say, “Woah there, tiger! Take it easy, we’re still in public!”

“Oh, gosh, I’m sorry… It’s just that… Oh, when it’s with you…” he seems to be lost in thought for a moment, gazing at you; “I just can’t help myself around you.” 

You laugh seductively and whisper to him, “Well, you just need to hold out ’til we get home and then you won’t need to restrain yourself at all.” 

He stares at you in awe, mouth slightly agape; “Do… Do you really mean that?”

“Of course,” you reply, kissing him on the cheek. 

“Oh… Oh my…” your body pressed tightly against his, you can feel something growing, pushing against your hips.

You smirk, and start moving in time to the music again, this time making sure to apply extra pressure, rubbing yourself against him teasingly, just enough to stimulate him. He gasps, looking around frantically; “Wh- I- what happened to what you said about being in public?” 

You lean into his ear. “Shhh, my love, we’re just dancing.”

“Right… Right… Yeah, just dancing.” He says, still blushing hard and now starting to tremble slightly. He puts his hands on your hips again, applying pressure to push them even harder against himself. He gyrates his hips slightly against you now, trying to stimulate himself further; he breathes hard, staring intensely at you, letting out stifled moans every now and again.

You dance and you hold him for that ambiguous amount of time that comes with experiences that you don’t want to end; finally, the music stops playing as no more songs are queued in the jukebox; he grabs onto your waist and murmurs “So, would you like to accompany me home?”

“Without a doubt,” you say, leaning in for another kiss. When you pull back, he looks panicked for a moment.

“Um… Could you… Could you please stand right here for a moment? And not move?” He says, adjusting you slightly so that your back is to a wall. He turns around, ducking behind you, hurriedly adjusts himself, and says “Okay! Okay. I’m ready to go now.”

You dash out of the bar, holding each other’s hands, laughing gleefully, occasionally taking a moment to playfully chase each other, always ending in a big, rough bear hug. These hugs start taking on a more and more flirtatious tone, as Karl just barely restrains himself from feeling you up on the street.

As you walk further away from downtown and closer to his home, he starts to feel emboldened by the lack of people nearby. Holding on tightly to your hand, he murmurs into your ear; “You drive me completely wild, you know that? You… You have just got to be the most stunning person I’ve ever met.”

You blush; “Oh, you’re just too much!” 

“I’m serious. I’m not exaggerating, either; you… You are divine. You are just so absolutely incredible…” he slips a hand around your waist. “How lucky am I that I get you all to myself?” You can see his erection starting to appear through his jeans again, but with no one around, he makes no attempt to hide it. He leans in to whisper to you, with a mischievous and seductive smile; “You have no idea what I’m going to do with you when we get home.”

You two pick up your pace, eager to get home as quickly as possible. You round the corner to his neighborhood, and bound up to the patio; Karl fumbles with the keys has he unlocks the front door, and upon it opening successfully, leans into the house and shouts “HELLO? HELLOOO? ANYONE HOME?”

Upon deciding firmly enough that there was no one else in the house, he holds the door for you, and he shuts and locks it behind you. In no time, he’s on top of you; you’re pressed to the wall of the front hallway, his left hand pinning your wrist to the plaster and his right hand slipping up your shirt.

He humps your leg desperately, overflowing with the desire that he’s suppressed all evening. He kisses you deeply, his tongue mingling with yours, occasionally grunting and moaning in his intense lust. He takes a moment away from feeling your chest to unbutton your shirt, from the top down, trying to get it off of you as fast as possible but still clumsy from the alcohol. 

After struggling with a button for too long, he drops to his knees to get a more clear look, undoing the rest of the buttons quickly, then wrapping his arms around you, feeling the bare skin of your back and kissing your stomach over and over.

“Oh my god… You’re so incredibly, amazingly, insanely perfect…! Every single part of you… How, how can anyone be so perfect?”

You blush. “N-no… That can’t be true.” You murmur shyly.

He pulls you to the ground with him. “Shhh… You know I wouldn’t lie to you.” He brings his lips to yours again, and before you know it you’re on the floor of the hallway, his hands cradling your head as you kiss each other deeply. He can’t restrain himself from rubbing his crotch against yours, the speed and firmness of which grows subtly with every second.

He moves his kisses away from your mouth, down to your neck, and then your chest and stomach. “Your body… it’s, it’s just incredible… Like, like the perfect person, designed just for me, mmph-“ he nuzzles his face into your lower belly, giving it several kisses while he strokes your chest. “Oh… You’re just so wonderful, so completely and utterly wonderful… I love you, oh, god, I love you so much!”

He brings his hand beneath your underwear and starts to gently rub the area around your clit, making you gasp. He rubs in small, slow circles as he resumes kissing your stomach; his kisses descend lower, and lower still, until he tugs down your pants, exposing you. 

He takes a moment to stop and stare, looking hungrily at the growing wet spot beneath your legs, and then kisses it gently, lingering there a moment to savor your scent. 

Suddenly, as if something snapped inside him, he voraciously tugs off your underwear and immediately presses his mouth into you, moving his tongue in long strokes up and down, making you shriek in overwhelmed pleasure; “Ah, aah~! Karl- Karl- wait- wait- that’s too-“

He pulls away from you with a satisfied grunt; “Mmmn, I’m sorry, my love, I just couldn’t wait anymore.” He resumes with more sensitivity this time, circling his tongue around your clit, then gently brushing it, alternating this with soft sucking.

The sensation is unbelievable. Your back arches uncontrollably and your thighs tremble with the intensity that only he is capable of giving you; you cry out his name over and over, gripping onto his hair and pushing him even harder into yourself, which he accepts graciously, wrapping his arms around your thighs, wanting to be as close to you as he possibly could be. 

He brings his tongue lower, teasing it around the opening; you can hear him breathing hard, letting out little moans in delight of your taste. Then, he slips his tongue inside, bringing it as deep as it can go, and you cry out and press his head even harder into you, ecstatic with the incredible intimacy of his every movement.

He wriggles his tongue around inside of you, moving his fingers over to stimulate your clit at the same time, humping the floor and whining out of absolute desperation. Every second the incredible pleasure builds and builds, until you reach the moment just before it overflows; your body tenses more and more, shaking harder and harder; until suddenly, it releases.

You scream, gripping on hard to his hair, your spine arcing and straightening jerkily as you’re consumed by a wave of ecstasy. You’re beyond the point of words; you just cry out in primal lust as Karl grips on hard to your thighs, looking at you with adoration and desire as you cum.

He sits up, undoing his belt and sliding his pants down, followed by his briefs; he lays his body over yours, placing his throbbing-hard cock right in between your legs; he caresses your face, staring at your blushing, sweaty face lovingly, and comes down to kiss you. You wrap your arms around him, pulling him as close to you as you can, kissing him feverishly, passionately, desperately.

You never once stop kissing him as he slides his cock inside, causing you both to whine in pleasure as your tongue is still entwined with his. He remains still for a moment, having completely filled you up, and then pulls away from your mouth with a gasp. He wraps both his hands around your head as he softly begins to pulse his cock in and out.

“Mmmh, you- you’re so incredible… So… so incredibly amazing- I, I love you… I love you so, so much,” he moans as his pace begins to increase.

“I love you too,” you say as you wrap your legs around his hips, allowing him to get even deeper inside you, gasping again as he fills you with the entire length of his dick. 

He squeezes both of his hands hard on your ass cheeks as he starts to lose himself to the sensation of being inside you; he gets rougher, causing you to yelp every time he thrusts in completely, and whines “Oh, oh, my love… You- you feel so good, so incredibly good, mmh- ah!” 

He leans down over you, fucking you hard and fast now, making your eyes roll back and reducing any speech to incoherent gasps and squeals; he runs his fingers through your hair, then grips on, pounding into you relentlessly.

“Oh, sweetheart… My love, are you gonna cum? I can feel how hard you’re starting to shake,” he observed. He was bringing you very close to the edge, but you were too overwhelmed to respond properly. You nod your head and make some incoherent noises of agreement, and involuntarily tighten your legs around his body.

“Oh, yes, my darling… Oh, yes, yes, yes, cum for me, please,” he moans, his pounding only getting harder and faster as he’s encouraged by your reaction.

It’s only seconds before he sends you over the edge, making his pounding slow, hard, and deep as you grab onto him, crying out in hysterical pleasure and shaking with your entire body. He moans, as well, desperately trying to keep himself from cumming along with you; no matter how badly he wanted to fill you up in that moment, he wanted even more to continue pleasuring you.

You two lay there for a moment, coming back to your senses slowly as you lay in a shaking, sweaty heap on the ground. After he catches his breath, he says in a low rumble, “Turn around for me, my love.”

You’re unable to oblige his request immediately, as your muscles are still weak from the shock of the orgasm; “Come on now, angel,” he says, grabbing your hand and helping you to sit up.

Still in a blissful daze, you move to be on your hands and knees, facing away from him; he wastes no time wrapping himself around you, caressing your sides, stomach, and chest, and placing his cock firmly in between your ass cheeks.

He touches you like he’s desperate to feel every surface on your body. He kisses you softly on the back of your neck, and croons “Oh, you are a dream come true.” You start gyrating your hips, sliding his dick through your cheeks, causing him to let out a high-pitched, unrestrained moan; “Oh, god, I can’t wait any more;” he lines up his cock, ready to thrust in at any time; “I need to take you again.”

You’re the one to take initiative this time, as you slip down onto his cock, letting him fill you up completely. He wails as you do this; “Oh, oh, baby…! That’s- oh, that’s, that feels so good, so, so good- ngGAH!” He shouts again as you start feverishly bouncing up and down on his cock, yearning to give him the same pleasure that he gave you.

“F-f-fuck, oh, ohgm- oh my god- oh my g- oh, ohfff- ah, ah-“ is all he can manage to sputter out as you ride his dick hard and fast. He grabs your ass as it unrelentingly slams against his body. “S-shit, holy sh-shit, I- I didn’t- I, I didn’t know anything- ah, mmmh- anything could feel this g-good! So good! S-so fucking- ah, ah! So fucking good!”

Suddenly, he holds your hips hard against his, preventing you from moving anymore. He pants hard, quietly moaning with every breath; “Oh… Oh, angel… It’s my turn.”

Your head is pushed to the floor as Karl grips your hair and starts pounding into you ferociously. He grunts with exertion and pleasure as he fucks you with every ounce of passion and desire he can muster; you wail, completely taken by the sensation of his cock.

“I’m- I’m so happy to have you all- all to myself- nngh; mine… Yes… Oh, yes… You’re mine… Isn’t that right?”

“Y-yEEESS!” You cry out, already being driven to the edge of cumming, your legs barely keeping your body up as you’re completely overtaken by the sensation of his ever-pounding cock. 

“Oh- oh, fffuck- yes, you- you’re mine- you’re mine- mmh, oh, oh god;” you can feel it building again; your thighs tremble violently as you prepare for another immense wave of pleasure to strike.

“Karl… Karl, I’m- I’m cumming, I’m, I’m- ah, ah AH AHHHH-“ you scream, driven to new heights of pleasure by the force of his cock slamming inside you, and you lose yourself completely to the incredible feeling.

You’re so overtaken by your orgasm you can barely perceive Karl moaning “Oh, oh god- I- I can’t- I- I- oooh, YEEEEESSS, YES, YES,” as he succumbs to the pleasure as well, filling you up with hot, creamy white cum.

You both collapse to the ground, him laying on top of your back, his cock still inside; for a few minutes, you lay there and breathe, coming back to consciousness, enjoying the warmth of each other’s skin.

He rolls off of you, coming to rest at your side; he rubs your cheek gently with his thumb, and says “Well… Maybe we ought to finally make our way over to a bed.” You giggle, nod, and kiss him; he stands, picking you up bridal-style, and carries you to bed.

**Author's Note:**

> I would like to mention that it is never clarified whether or not Karl removes the "Birthday King" crown. Therefore, whether he was wearing it during the sex or not is at your discretion.


End file.
